FIG. 1 is a diagram of an ad hoc network. An ad hoc network comprises nodes, such as mobile stations that can communicate directly with each other, without the use of a centralised access point. In such a network all nodes behave as routers. Since the nodes are free to move randomly the topology of the network changes with time. Data from a source node (1) (the terminal that is sending data) is sent to a destination node (2) (the terminal that is receiving the data), via intermediate nodes which forward the data from the source node to the destination node. Determining the route by which data is sent from the source node to the destination node is achieved by selecting which intermediate nodes are used to forward the data. This is known as routing.
Different routing protocols for ad hoc networks are currently known. These routing protocols can be classified as: ‘table driven’ and ‘on demand’ routing, otherwise known as ‘proactive’ and ‘reactive’ routing, respectively. In table driven protocols, each node maintains one or more tables containing outing information to other nodes in the network. These tables are updated using periodic transmissions between nodes so as to change with the topology of the network. Examples of table driven routing protocols include Dynamic Destination Sequenced Distance Vector Routing Protocol (DSDV), Global State Routing (GSR) and Wireless Routing Protocol (WRP). In contrast, on demand routing protocols invoke route discovery mechanisms only when a route is needed. Examples of on demand routing protocols include Ad Hoc On Demand Distance Vector Routing (AODV), Dynamic Source Routing (DSR), Temporally Ordered Routing Algorithm (TORA) and Associativity Based Routing (ABR).
In the DSDV protocol, every mobile station maintains a routing table that lists all available destinations, the number of hops to reach the destination and the sequence number assigned by the destination node. The sequence number is used to distinguish old routes from new ones and thus avoid the formation of loops. The mobile stations periodically transmit their routing tables to their immediate neighbours. A station also transmits its routing table if a significant change has occurred in its table from the last update sent. Therefore, the update is both time driven and event driven. The routing table updates can be sent in two ways; either by sending the full routing table to the neighbours or by incrementally updating entries that have changed since the last update.
Ad hoc On-demand Distance Vector routing (AODV) is an improvement on the DSDV algorithm. AODV minimises the number of broadcasts by creating the routes on demand as opposed to DSDV that maintains the list of all the routes.
To find a path to the destination node, the source node broadcasts a route request message. The neighbouring nodes in turn broadcast the message to their neighbours until it reaches an intermediate node that has recent route information about the destination node, or until the message reaches the destination. A node discards a route request message that it has already seen. The route request message uses sequence numbers to ensure that the routes are loop free and to ensure that if the intermediate nodes reply to the route request message, they will reply with the most recent information only.
When a node forwards a route request message to neighbouring nodes, it also records in its tables the node from which the first copy of the request came. This information is used to construct the reverse path for the route reply, or acknowledgement message. AODV uses only symmetric links because the route reply message follows the reverse path of the route request message. As the route reply message traverses back to the source node, the nodes along the path enter the forward route into their tables.
Mobile device positioning is an important requirement of any telecommunications system and is an existing feature in both ad hoc and cellular networks. The Federal Communications Commission (FCC) requires wireless service providers to support a detailed positioning mechanism. Positioning information of a mobile station may be used for many purposes:                pricing of calls may be based on the position of a mobile station, whereby calls made from the home area, for example, may be cheaper;        when an emergency call is placed from a mobile station, it is possible to determine the position of the mobile station;        the user of a mobile station may need information about his/her location e.g. when travelling;        the authorities can use the positioning information to locate a stolen mobile station or to trace a missing person, for example.        
Generally, positioning methods are based on the propagation characteristics of a radio wave signal sent to or from the mobile station, using the delay and direction of the signal between the transmitter and the receiver to determine a position. Therefore, the accuracy and complexity of such methods are inclined dependent on the characteristics of the radio channel. Many different positioning methods have been developed for mobile positioning. They can be categorized based on the way they utilize the radio signal characteristics for determining the location of the mobile station.
Classifications of methods used to determine position include:                Cell_ID-based positioning        Round Time Trip (RTT)        Time Of Arrival (TOA)        Different Time Of Arrival (DTOA)        Angle Of Arrival (AOA)        Signal strength-based such as Reference Node-Based        Positioning (also called local positioning)Positioning methods may also incorporate any combination of these methods.        
In a TOA method, the location calculation is based on the propagation delay of a signal from a transmitter to a receiver. By measuring the time of arrival of signals from three transmitters at a receiver, the position of the receiver can be calculated using triangulation techniques that are well known in the art.
The above-mentioned ways of calculating the position of a mobile station can be utilized in various systems such as cellular systems, purely location systems, or any similar systems. Presently, the most popular positioning system is Global Positioning System (GPS). Positioning features are extending to the cellular systems such as Global System for Mobile Communications (GSM), Universal Mobil Telecommunication System (UMTS) and International Mobile Telecommunications 2000 (IMT2000).
GPS is the most popular position location system due to its accuracy and worldwide availability. GPS consists of a constellation of satellites in orbit above the Earth. GPS position determination is based on the arrival times, at a receiver at the mobile station, of precisely timed signals from the satellites that are above the user's radio horizon. Each satellite uses an atomic clock to record the time at which the signal is sent. An accurate clock at the receiver measures the time delay between the signals leaving the satellites and arriving at the receiver. This allows the calculation of the distance of the mobile station to each satellite. If three satellites are visible to the receiver, triangulation can be used to find the location of the mobile station. If a fourth satellite is used, the receiver may also calculate its latitude. Since the clock in the receiver is not as accurate as the atomic clocks in the satellite the calculation of the distance from each satellite will have a standard error, which prevents the spheres calculated during triangulation from intersecting at the same point. The receiver therefore can calculate the distance adjustment that will cause the four spheres to intersect at one point. This allows it to adjust its clock to adjust its measure of distance. For this reason, a GPS receiver actually keeps extremely accurate time, on the order of the actual atomic clocks in the satellites. Currently, the Standard Positioning Service offered by GPS provides a positioning accuracy of 100 meters horizontally and 156 meters vertically and time transfer accuracy to UTC within 340 nanoseconds (95 percent).